Solubilized collagen fibers and method for producing the same

ABSTRACT

Provided are novel solubilized collagen fibers with which solubilized collagen can be obtained by instantaneous uniform dissolution in water at the time of use. The solubilized collagen fibers are formed from a solubilized collagen solid content of 66 to 87 wt %, buffer salt content of 2 to 6 wt %, water content of 10 to 22 wt %, and a residual hydrophilic organic solvent content of a trace amount of up to 6 wt % (totaling 100 wt %). The solubilized collagen fibers have an average fineness of 3 to 10 dtx, an isoionic point of 4.5 to 5.0, a water content of 10 to 22 wt %, and residual hydrophilic organic solvent content of a trace amount of up to 6.0 wt %. The solubilized collagen fibers are present uniformly in the direction of fiber length. The buffer salt is selected from sodium citrate, sodium lactate, and sodium phosphate.

TECHNICAL FIELD

The present invention relates to solubilized collagen fibers and amethod for producing the same.

BACKGROUND ART

Solubilized collagen has excellent moisture retention properties.Compared with other bio-derived moisturizing agents such as hyaluronicacid, solubilized collagen is produced in high yield, and relatedproducts are therefore inexpensive. This point is attracting muchattention, and the use of solubilized collagen as a raw material forcosmetics is highly anticipated.

Besides the aforementioned properties as a moisturizing agent, thefollowing properties of products that contain solubilized collagen arealso attracting attention. Namely, the ability to promote the adhesionand proliferation of cells, low antigenicity, high biocompatibility, andfavorable biodegradability and the like.

By utilizing these properties, solubilized collagen can be usedeffectively in all manner of applications including cosmetics andmedical materials. In terms of the use of collagen for these purposes,the use of collagen in a variety of different forms has beeninvestigated depending on the intended application, including aqueoussolutions, fibrous materials, films, sponges and gels.

It had been thought that with high-concentration solubilized collagen,the collagen should be able to be dissolved uniformly andinstantaneously at the time of use. However, it was found that thecollagen could not be dissolved uniformly and instantaneously in a watermedium at the time of use, and that therefore obtaining the type ofcosmetics that users had been anticipating was problematic.

Techniques relating to this aspect include the following.

(1) A method for producing a high-concentration solubilized collagen byusing a freeze drying method as a technique for removing water.

(2) A method for producing a granulated or powdered solubilized collagendried product (weight concentration: 95% or greater) by injecting asolubilized collagen solution (weight concentration: 3 to 10%) through anozzle into a volatile hydrophilic organic solvent medium to form athread-like product or film-like product within the medium, subsequentlydrying this thread-like or film-like product in a drying step to removethe organic solvent and water content, and then chopping or crushing thethus obtained dried product (Patent Document 1: JP 06-228505 A).

The above term “crushing” means to finely grind the product. Performingthis fine grinding is difficult. Because this fine grinding cannot beachieved, when the dried product is dissolved in water, problems tend toarise, including the formation of lumps, and an inability tosatisfactorily complete the dissolution operation.

(3) A method for producing a collagen molded product having excellentshape retention and environmental resistance by deaerating an aqueouscollagen solution, forming a film, treating the thus obtained film withan aqueous aldehyde solution, drying the treated film, subsequentlythermoforming the film into a molded product of the desired shape, andthen subjecting the obtained molded product to a crosslinking treatmentusing an inorganic crosslinking agent and/or an organic crosslinkingagent has been proposed (Patent Document 2: JP 06-200047 A). Thisinvention employs a crosslinking treatment in obtaining the collagenmolded product, and uses this crosslinking as a technique for obtaininga stabilized collagen molded product. Accordingly, there is no intentionthat this molded product is dissolved in water for subsequent use. Evenan intention to dissolve the product in water is unreasonable from atechnical standpoint.

(4) A powdered collagen produced by adjusting the pH of a collagensolution to a value in the vicinity of the isoionic point, and thensubjecting the collagen solution to a spray-drying treatment as auniform dispersion with a concentration of 3 to 10%, and a method forproducing a powdered collagen by adding a basic solution to ahigh-concentration collagen solution to adjust the pH to a value in thevicinity of the isoionic point, subsequently adding deionized water toobtain a solution with a concentration of 3 to 10%, stirring to obtain auniform dispersion, and then spray-drying the dispersion are also known(Patent Document 3: JP 08-27035 A). However, if this invention is viewedfrom the perspective of the yield of the powdered collagen thatrepresents the product, then various problems are apparent, includingpoor production efficiency, the generation of lumps during dissolution,and an inability to achieve the anticipated solubility.

(5) By adding a plasticizer to a collagen dispersion using aconventional method, performing kneading and degassing, subsequentlydrying the dispersion to form a collagen film, and then subjecting thefilm to an appropriate heat treatment or ultraviolet irradiationtreatment, the collagen can be imparted with hot water solubility. Theheating is disclosed as being typically 50° C. to 70° C., and preferably50° C. to 60° C. (Patent Document 4: JP 09-124804 A).

The invention described above enables the actual production ofhigh-concentration solubilized collagen. However, using this techniqueto enable collagen to be dissolved uniformly and instantaneously in coldwater is problematic. The use of a high-concentration solubilizedcollagen to obtain a water-soluble collagen is impossible.

(6) A collagen pack invention (Patent Document 5: JP 4,353,850 B, JP2005-325056 A).

Although this invention discloses a novel collagen pack obtained using asolubilized collagen aqueous solution, it is not directly related to theuse of collagen as a cosmetic.

Next, an invention was proposed for a conjugated solubilized collagenpowder in which trehalose coexists within the particles (Patent Document6: JP 2009-67703 A). In this invention, an aqueous spraying liquidcontaining the solubilized collagen and trehalose is prepared, and thisliquid is then spray-dried to obtain a solubilized collagen powder. Thetrehalose coexists within the target product, and by also adding anamphoteric surfactant or a glycol compound, the hydrophilicity and thesensation of the product can be improved. However, this product does notcontain solely collagen as the main component. The powder cannot be usedas a cosmetic which contains collagen as the main component andundergoes uniform dissolution of the water-soluble collagen almostinstantaneously at the time of use, which is the original objective forthe inventors of the present invention.

With the intention of developing a product that could be dissolveduniformly and instantaneously at the time of use to prepare awater-soluble collagen, and then using this product as a cosmetic, theinventors of the present invention thought that the production ofsolubilized collagen fibers for the cosmetic was important, andconducted various investigations aimed at obtaining solubilized collagenfibers for cosmetics.

If the collagen can be incorporated at high concentration within anaqueous solution, then this solution can be used as a material forobtaining solubilized collagen fibers for cosmetics. Based on thisthinking, the inventions described below were developed.

(1) An invention relating to a fibrous solubilized collagen cosmeticthat uses a solubilized collagen solution as a raw material

Pig skin (including hair) was used as a raw material, and followingcompletion of a hair removal liming step, the skin was treated inside amixer drum.

The insoluble collagen was treated under alkaline conditions to producean acidic solution of soluble collagen. The acid solution of thesolubilized collagen was discharged into isopropyl alcohol from a nozzlehaving 1,000 discharge holes, and spun to solidify the collagen into afibrous form. The solidified product was able to be obtained as a fiberbundle containing 1,000 continuous strands.

The product was extracted as a collagen fiber bundle immersed inalcohol, was cut to a length of approximately 1 meter, and was then hungfrom a stainless steel rod inside a clean bench (sterilized workapparatus) and dried (for one day and night). The folded portion wherethe fiber bundle was hung over the stainless steel rod was compressed bythe weight of the fiber bundle, causing the fibers to adhere to eachother. It was discovered that drying the fibrous solubilized collagen isdifficult.

When the fibrous solubilized collagen was evaluated, it was found thatnot only was the raw material an acidic solution, but the fibers werevery thick (60 dtx) and the rate of dissolution was extremely slow,meaning the fibers were unsuitable for obtaining a fibrous solubilizedcollagen cosmetic. Unfortunately, this line of thinking was abandoned.Although this line of thinking was unsuccessful, it was discovered thatthe method of drying a collagen fiber bundle in a state that had beenimmersed in a hydrophilic organic solvent such as an alcohol had a largeeffect on the results. This finding is utilized in the presentinvention.

(2) An invention relating to solubilized collagen short fibers forcosmetics

Considering the fact that a satisfactory drying operation could not beperformed in the fibrous solubilized collagen cosmetic described in (1)above, it was decided to test a fibrous solubilized collagen cosmetic inthe form of solubilized collagen short fibers.

An insoluble collagen was treated under alkaline conditions to producean acidic solution of solubilized collagen. In order to improve thesolubility of the solubilized collagen cosmetic that represents theproduct, a sodium salt of an organic acid (buffer) and sodium hydroxidewere added to the acidic solution to make the solution neutral (a pH ofapproximately 7). Initially, sodium citrate which has a powerfulbuffering action was used, but because it tended to precipitate in thealcohol, this was changed to sodium lactate. Following conversion of thecollagen to fibers, when the fibers were dissolved in a neutral aqueousliquid, because the isoionic point of 4.8 was not passed duringdissolution, solubilized collagen fibers that exhibited good solubilitywere able to be obtained.

The solubilized collagen solution that had been converted to a neutralstate was discharged into isopropyl alcohol from a nozzle having 1,000discharge holes, and solidified into a fibrous form. The solidifiedproduct was able to be obtained as a fiber bundle containing 1,000continuous strands. At the same time, the lipids dissolved in thealcohol, meaning a delipidation effect was also achieved.

A propeller was rotated immediately beneath the nozzle, so that prior tosolidification as fibers, the collagen fibers were cut to form shortfibers.

In order to dry the thus obtained collagen short fibers, the collagenshort fibers were adhered to the surface of a stainless steel net, andwere left to dry inside a clean bench. When leaving the fibers to standinside the clean bench, it was not possible to arrange the adheredsolubilized collagen short fibers in a uniform thin state having aconstant thickness, and in those portions where the fibers were adheredthickly, the drying was slow, and the fibers were more likely to adhereto each other.

The content of the solubilized collagen short fibers was substantiallypure collagen containing approximately 15% of water, but did alsoinclude small amounts of the sodium lactate or the like used as abuffer, and the isopropyl alcohol used as the organic solvent in thespinning bath. The fineness of the solubilized collagen fibers wasapproximately 20 dtx (the number of grams per 10,000 m of fiber). It wasdiscovered that a dissolution time of approximately 30 seconds could beachieved (Patent Document 7: JP 2005-306736 A, JP 4,401,226 B).

(3) Production of solubilized collagen fibers for cosmetics (PatentDocument 8: JP 2006-342472 A, JP 4,628,191 B)

The solubilized collagen fibers for cosmetics were obtained by preparinga raw material solution of solubilized collagen having an isoionic pointof pH 5.0 or less, discharging the solution from a nozzle into isopropylalcohol in the same manner as that described above, thus forming a fiberbundle of the solubilized collagen fibers for cosmetics, performingspinning and drawing of the fibers, immersing the fibers in ahydrophilic organic solvent, and then removing the water content andorganic solvent from the fibers. Initially, a continuous roller dryingprocess was adopted in which drying was performed by passing thesolubilized collagen fiber bundle continuously through a winding device21 while air was blown across the fibers (FIG. 2, left). In this case,contrary to expectations, crimping of the collagen fibers did not occur,fiber separation defects (adhesion of the fiber bundle) tended to occur,and the removal of the water content and organic solvent wasunsatisfactory, resulting in poor drying efficiency, meaning a stabledrying operation could not be achieved.

Next, an attempt was made to remove the water content and organicsolvent by suspending the solubilized collagen fiber bundle inside aclean bench and then blowing air across the fibers. Because thesolubilized collagen fiber bundle was not moved in a continuous manner,batch drying was used (this batched hanging drying is illustrated inFIG. 2, right). In this case, crimping was able to be achieved to someextent, and an improvement in fiber separation was also observed.Unfortunately, some non-uniformity in the removal of the water contentand organic solvent was observed in portions of the fibers. Further,during the batch drying, adhesion of the solubilized collagen fiberbundle tended to occur in some portions. The fiber bundle was placedbetween two drums each having a plurality of wires embedded therein, afiber opening (where the fiber bundle is separated into individualfibers) was performed by rotating the drums so that the wires did notmake contact with each other, thus forming a fibrous state. Satisfactoryfiber opening could not be achieved, and the drying treatment wasinadequate, and those portions were the fibers had adhered were cut awayand not used. At the time of packaging, the solubilized collagen fiberswere converted to a rounded fibrous state, and subsequently collectedand packaged. The thus obtained solubilized collagen fibers had afineness of 10 dtx or less (the number of grams per 10,000 m of fiber),and were able to be dissolved uniformly in water within 30 seconds.

In this case, the amount of residual water content and the like withinthe fibers could not be made uniform, crimping could not be applieduniformly across the entire solubilized collagen fiber bundle, fiberseparation was unable to be achieved for the entire solubilized collagenfiber bundle, the water content and organic solvent could not be removeduniformly by the drying treatment, and partial defects occurred such asadhesion of the fibers in some portions, meaning inadequacies wereobserved in the product. However, compared with the aforementioned caseof the short fibers, the results were tolerable as a solubilizedcollagen for use as a cosmetic.

(4) Moisturizing agent-containing solubilized collagen fibers (PatentDocument 9: JP 2008-214226 A)

Solubilized collagen fibers encapsulating a moisturizing agent that issolid at normal temperature and selected from hyaluronic acid andalginic acid. The solubilized collagen fibers are produced by preparinga solubilized collagen aqueous solution A containing the solubilizedcollagen having an isoionic point of pH 5.0 or less and the moisturizingagent and having a larger pH than the isoionic point of the solubilizedcollagen, subsequently discharging the aqueous solution into an organicsolvent in a thread-like form, solidifying and spinning the solubilizedcollagen into a fibrous state, and then drying the fibers. Because themoisturizing agent selected from hyaluronic acid and alginic acid isencapsulated within the solubilized collagen, a product in which thesolubilized collagen is the main component cannot be obtained, andtherefore this invention differs from the present invention.

Conventional solubilized collagen fibers for use in cosmetics suffer thetypes of problems outlined above. To summarize, the specific problemsare as follows.

When the collagen fiber bundle obtained following the drying step isobserved, crimping has not been applied in some portions, and fiberseparation defects (adhesion of the fiber bundle) exist in someportions. These problems are caused because portions exist in which theremoval of the water content and the organic solvent is unsatisfactory,causing adhesion of the fibers and the like. Conventionally, thoseportions of the solubilized collagen fibers that are free from theseproblems have had to be selected for subsequent use.

In conventional solubilized collagen fibers, because the drying stepdoes not function satisfactorily, the water content exists in anon-uniform manner within the fibers, which causes problems. In order toaddress this problem, the development of an invention that enables theproduction of a solubilized collagen fiber bundle and solubilizedcollagen fibers in which crimping is applied to the entire fiber bundle,fiber separation defects (where the fiber bundle undergoes adhesion) donot exist, and removal of the water content and the organic solventoccurs uniformly along the entire length direction of the solubilizedcollagen fibers, meaning the fibers do not adhere to one another, isvery important, and the inventors considered techniques for addressingthese problems.

PRIOR ART DOCUMENTS

Patent Document 1: JP 06-228505 A

Patent Document 2: JP 06-200047 A

Patent Document 3: JP 08-27035 A

Patent Document 4: JP 09-124804 A

Patent Document 5: JP 4,353,850 B, JP 2005-325056 A

Patent Document 6: JP 2009-67703 A

Patent Document 7: JP 2005-306736 A, JP 4,401,226 B

Patent Document 8: JP 2006-342472 A, JP 4,628,191 B

Patent Document 9: JP 2008-214226 A

DISCLOSURE OF INVENTION Problems Invention Aims to Solve

An object of the present invention is to provide novel solubilizedcollagen fibers with which solubilized collagen can be obtained byinstantaneous and uniform dissolution in water at the time of use.

Specifically, an object of the present invention is to providesolubilized collagen fibers in which crimping is applied to the entiresolubilized collagen fiber bundle and in which fiber separation defects(where the fiber bundle undergoes adhesion) do not exist, by obtainingsolubilized collagen fibers in which the residual water content andorganic solvent that remains following drying exists uniformlythroughout the fibers.

Means for Solution of the Problems

(1) As a result of intensive research, the inventors of the presentinvention discovered that the reason that crimping is not applied insome portions, that separation defects (where the fiber bundle undergoesadhesion) exist, and that portions in which the removal of the watercontent is inadequate exist within conventional solubilized collagenfibers is due to a lack of investigation of the operations wherein thesolubilized collagen is subjected to a spinning and drawing step bydischarging the solubilized collagen aqueous solution into an organicsolvent in a thread-like form, spinning the fibers into a fiber bundleand then drawing the fibers by winding the spun solubilized collagenfiber bundle, and the drawn solubilized collagen fiber bundle issubsequently immersed in a hydrophilic organic solvent and then removedfrom the hydrophilic organic solvent and dried. The inventors discoveredthat by improving the operation of the drying step of removing the waterand hydrophilic organic solvent from the solubilized collagen fiberbundle, the aforementioned object of the present invention could beachieved. Specific aspects of the present invention are described below.

(2) In conventional methods, the solubilized collagen fibers forcosmetics are suspended from a suspension device with the solubilizedcollagen fiber bundle still containing large amounts of water andorganic solvent, and air is then blown across the fibers to vaporize theorganic solvent and the water.

When air is blown across the fibers, it is very difficult to strictlycontrol the temperature of the sterilized air at 30° C. or lower, andpreferably approximately 20° C., and therefore the drying hasconventionally been performed without strict controls on the heatingconditions. Further, it has not been possible to completely preventdenaturation of the solubilized collagen fibers, and hanging the fibersfrom a suspension device has meant that the existence of non-uniformityin the amount of organic solvent and water within the fibers has beenunavoidable. The portions of the solubilized collagen fibers that makecontact with the suspension device, and the portions in the vicinity ofthe point of contact, are pulled by the weight of the solubilizedcollagen fibers, and therefore the fibers are pulled close together andadhere to one another upon drying, meaning they cannot be used as acosmetic. Further, the application of the air flow to the fibers is alsonon-uniform, and therefore in those areas where the air flow makesinadequate contact, the fibers tend not to move, and are thus difficultto separate. It is thought that these are the reasons that crimping isnot applied to some portions, that separation defects (where the fiberbundle undergoes adhesion) tend to exist, and that portions in which theremoval of the water content is inadequate tend to exist.

(3) Considering the above circumstances, the inventors reached theconclusion that a drying method that pays due attention to the followingpoints should be appropriate. Specifically, the content of the dryingoperation is as follows.

(a) Prior to vaporizing the organic solvent and the water content,performing a physical operation from the periphery of the solubilizedcollagen fiber is effective in removing preliminary amounts of theorganic solvent and water. As a result, the drying operation for theorganic solvent and the water content can be performed undercomparatively moderate conditions. Because the weight of the solubilizedcollagen fiber bundle is also reduced, a more moderate operation can beused to move the solubilized collagen fiber bundle. Further, even ifheat is applied from the periphery of the solubilized collagen fiberbundle, if air for which the temperature has been strictly controlled to30° C. or lower is supplied from the periphery, then solubilizedcollagen fibers and a solubilized collagen fiber bundle can be obtainedin which the organic solvent and the water content are distributedevenly between the inside and the outside of the solubilized collagenfiber bundle, and distributed evenly along the length direction of thesolubilized collagen fiber bundle. As a result, solubilized collagenfibers can be obtained in which crimping has been applied to the entiresolubilized collagen fiber bundle, fiber separation defects (where thefiber bundle undergoes adhesion) do not exist, and removal of the watercontent has been performed across all of the fibers.

(b) By completing an apparatus that incorporates the techniquesdescribed above, the above object can be achieved.

When subjecting the solubilized collagen fiber bundle and thesolubilized collagen fibers to the removal treatment, nip rollers areinstalled at the supply portion where the solubilized collagen fibersare introduced to the processing operations, a portion of the watercontent and the organic solvent contained within the solubilizedcollagen fibers is squeezed from the solubilized collagen fibers alongthe entire length of the fibers, the solubilized collagen fiber bundleis subsequently introduced into a drying tube, sterilized air that hasbeen controlled to a temperature of 30° C. or lower is forcibly blownthrough the tube to form a moving bed of air, and this moving bed of airis used to move the solubilized collagen fiber bundle for use incosmetics, which is reduced in weight due to the removal of a portion ofthe water content and the organic solvent, enabling the production ofsolubilized collagen fibers and a solubilized collagen fiber bundle inwhich the organic solvent and the water content are distributeduniformly from the inside to the outside of the solubilized collagenfiber bundle, and along the length direction of the solubilized collagenfiber bundle.

(c) When the properties of the solubilized collagen fiber bundle areanalyzed at the outlet of the drying tube upon completion of the dryingoperation, the following properties are observed.

The components contained within the solubilized collagen fibers and theamounts of those components include a solubilized collagen solid contentof 66 to 87 wt %, a buffer salt content of 2 to 6 wt %, a water contentof 10 to 22 wt %, and a residual hydrophilic organic solvent content ofa trace amount to 6 wt % (totaling 100 wt %). The average fineness ofthe solubilized collagen fibers is 3 to 10 dtx, the isoionic point is4.5 to 5.0, and the aforementioned water content of 10 to 22 wt % andthe residual hydrophilic organic solvent content of a trace amount to 6wt % exist uniformly along the length direction of the fibers.

This uniform distribution along the length of the fibers is the key toresolving the problems outline above.

The buffer salt is selected from among sodium citrate, sodium lactateand sodium phosphate.

The buffer salt is used as a pH modifier when converting the insolublecollagen to solubilized collagen, and acts effectively when dissolvingthe solubilized collagen fibers in water. In other words, the buffersalt is an important component in the solubilized collagen fibers of theinvention.

(4) A method for producing solubilized collagen fibers that includes thedrying step described above is described below.

(a) A method for producing solubilized collagen fibers that comprises:(i) a step of decomposing insoluble collagen fibers under alkalineconditions and extracting a solubilized collagen aqueous solution, and astep of performing pH modification to prepare a solubilized collagenaqueous solution that functions as a solubilized collagen fiber rawmaterial: namely, a step of subjecting a product obtained by decomposinga skin sample containing insoluble collagen fibers under alkalineconditions to a neutralization and desalting treatment, separating theneutralized and desalted skin sample, and subsequently extracting asolubilized collagen aqueous solution having an isoionic point of pH 5.0or less, and a step of adjusting the pH of the solubilized collagenaqueous solution in the presence of a buffer to a value within a rangefrom 6.0 to 7.5 which is greater than the isoionic point, thus preparinga solubilized collagen aqueous solution that functions as a solubilizedcollagen fiber raw material; (ii) a step of subjecting the solubilizedcollagen aqueous solution that functions as the solubilized collagenfiber raw material to spinning and drawing to produce a solubilizedcollagen fiber bundle: namely, a step of discharging the solubilizedcollagen aqueous solution obtained in (i) above into an organic solventin a thread-like form, spinning the solubilized collagen into a fiberbundle, drawing the spun solubilized collagen fiber bundle by winding,and then immersing the drawn solubilized collagen fiber bundle in ahydrophilic organic solvent; and (iii) a step of drying the solubilizedcollagen fiber bundle obtained in (ii) to produce solubilized collagenfibers for cosmetics: namely, a step of drying the solubilized collagenfiber bundle to produce the targeted solubilized collagen fibers bypassing the above solubilized collagen fiber bundle through nip rollers,introducing the resulting solubilized collagen fiber bundle having areduced water content and a reduced concentration of the hydrophilicorganic solvent into a drying tube, forming a moving bed of air insidethe tube by blowing sterilized air having a temperature of 30° C. orlower and a humidity of 70% RH or lower into the tube, using the movingbed of air to move and dry the solubilized collagen fiber bundle insidethe tube, and then extracting the solubilized collagen fiber bundle fromthe tube.

(b) A method for producing solubilized collagen fibers that furthercomprises a step of opening the fibers of the dried collagen fiberbundle obtained in (iii) above to form a fibrous state.

(c) The step (1) in (a) above may also be performed in the mannerdescribed below. The steps (ii) and (iii) may be the same as thosedescribed for (a).

(i) A step of decomposing insoluble collagen fibers using a proteindegrading enzyme (protease) and extracting a solubilized collagenaqueous solution, and a step of performing pH modification to prepare asolubilized collagen aqueous solution that functions as a solubilizedcollagen fiber raw material: namely, a step of adding an alkali to aproduct containing collagen, obtained by decomposing a proteincontaining insoluble collagen using a protease and having an isoionicpoint of 7 to 8, to adjust the pH of the product to 9 to 10, using acarboxylic anhydride to succinylate the solubilized collagen and reducethe pH to 5 or less, subsequently precipitating and separating thesolubilized collagen, and then adding an alkali in the presence of abuffer to adjust the pH to a value within a range from 6.0 to 7.5 whichis greater than the isoionic point.

Effects of the Invention

According to the present invention, a solubilized collagen fiber bundleand solubilized collagen fibers can be obtained in which crimping hasbeen applied to the fibers, fiber separation defects (where the fiberbundle undergoes adhesion) do not exist, a portion of the water contenthas been removed, with the residual water content existing uniformlythroughout the fibers, and fiber adhesion does not exist.

The components contained within the solubilized collagen fibers and theamounts of those components include a solubilized collagen solid contentof 66 to 87 wt %, a buffer salt content of 2 to 6 wt %, a water contentof 10 to 22 wt %, and a residual hydrophilic organic solvent content ofa trace amount to 6 wt % (totaling 100 wt %). Solubilized collagenfibers can be obtained in which the average fineness of the solubilizedcollagen fibers is 3 to 10 dtx, the isoionic point is 4.5 to 5.0, andthe aforementioned water content of 10 to 22 wt % and the residualhydrophilic organic solvent content of a trace amount to 6 wt % existuniformly along the length direction of the fibers. Accordingly, it wasclear that the above method for producing solubilized collagen fiberscould be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram illustrating one example of anapparatus for spinning and drawing a solubilized collagen fiber bundlefor cosmetics, and then immersing the fiber bundle in a hydrophilicorganic solvent in accordance with the present invention.

FIG. 2 is a diagram illustrating conventional drying devices.

FIG. 3 is a diagram illustrating a drying apparatus of the presentinvention.

EMBODIMENTS OF THE INVENTION

Collagen is defined as a protein or glycoprotein having at least apartial helical structure (collagen helix). Collagen occurs as a triplehelix composed of three polypeptide chains, wherein each polypeptidechain, which has a molecular weight of approximately 100,000, has aglycine residue every third position, and other frequently occurringamino acid residues include proline residues and hydroxyprolineresidues. Collagen is a protein that exists within all multicellularorganisms, and can be extracted in large amounts from the tissues, andparticularly the skin and bones, of invertebrates and vertebrates.

Due to differences in the structure of the collagen molecule, 19different types of collagen have been reported to exist, and even forcollagens classified as the same type, a plurality of differentmolecules may sometimes exist.

Collagen of types I, II, III and IV are mainly used as biomaterial rawmaterials. Type I exists in almost all connective tissue, and is thecollagen type that exists in the largest quantity in living organisms.In mammals, type I collagen exists in large amounts in tendons, thedermis and bones, whereas in fish, besides the above tissues, type Icollagen also exists in a large amount in the scales. In an industrialsetting, collagen is often extracted from these regions.

Collagen fibers are self assemblies of the above collagen molecules, andhave a specific fiber structure in which the collagen molecules arepacked in series and in parallel. In an industrial setting, solubilizedcollagen can be obtained from the collagen fibers within tissue using anacid, an alkali or a protease.

When heat is applied to collagen, the triple helix structure of thecollagen loosens, and a heat-denatured product is obtained in which eachof the polypeptide chains form a random coiled shape. The temperature atwhich this type of structural change occurs within the collagen istermed the denaturation temperature. The denatured product is calledgelatin. Compared with collagen, gelatin has a lower viscosity whenconverted to an aqueous solution. Further, gelatin is also known to havea high sensitivity relative to in vivo proteases.

The denaturation temperature for collagen is lowest when the collagen isin solution form. Further, collagen is generally obtained from abiological raw material, and it is said that the denaturationtemperature of such biologically obtained collagen is closely related tothe temperature of the living environment of the source organism. Thecollagen denaturation temperature in aqueous solution form isapproximately 38° C. for collagen from mammals. Fish collagen generallyhas a lower denaturation temperature than that of mammals, andparticularly in the case of cold current fish such as salmon, thetemperature may fall below 20° C. in some cases. When treating collagen,performing the treatment at a temperature of 30° C. or lower, andpreferably 20° C. or lower, indicates specifically that the treatmentmust be performed at a temperature below the denaturation temperature.

The raw material for the solubilized collagen fibers of the presentinvention is the collagen described above. This type of collagen isinsoluble collagen, is contained within the skin tissue and other organsof animals such as cows, pigs, birds and fish, and is obtained fromtissues that contain such insoluble collagen.

The inventors of the present invention initially started their researchinto collagen production with the aim of effectively utilizing the splitleather generated as a by-product during the production of leather. Thissplit leather can be used as the raw material.

Subsequently, as leather production shifted to tanning productionmethods (methods that use wet blue and wet white for leatherproduction), split leather was no longer generated.

The tissues containing insoluble collagen described above are now usedas the raw material for the purpose of producing collagen.

Examples of raw materials that can be used for the solubilized collagenfibers for cosmetics include mammal hides, and tissue derived fromaquatic organisms such as fish skin and fish scales.

By selecting the raw material used for obtaining the collagen, adifference is observed in the denaturation temperature of the obtainedcollagen. When the raw material is in a dried state, there are noparticular differences in the handling methods used, regardless of theraw material from which the solubilized collagen is derived. Currently,because of issues relating to BSE, the use of bovine-derived insolublecollagen tissue is undesirable, and the use of either porcine-derivedcollagen or collagen derived from an aquatic organism such as fish ispreferable.

Recently, the production of collagen from synthetic peptides isgarnering much attention as a potential material that suffers no dangerof BSE infection. A novel polypeptide of the present invention comprisesa peptide unit having an amino acid sequence represented by formula (1)shown below, and a peptide unit having an amino acid sequencerepresented by formula (2) shown below.

-Pro-X-Gly-  (1)

-Y-Z-Gly-  (2)

In these formulas, X and Z may be the same or different, and eachrepresents Pro or Hyp, and Y represents am amino acid residue having acarboxyl group (such as Asp, Glu or Gla).

The ratio (molar ratio) between the above peptide unit (1) and thepeptide unit (2) is within a range from approximately (1)/(2)=99/1 to1/99. The polypeptide may also support apatites (see JP 4,303,137 B).

Examples of the collagen used as the raw material for the solubilizedcollagen fibers of the present invention include pig skin that hasundergone alkali solubilization, and pig skin that has undergone enzymesolubilization and succinylation to adjust the isoionic point to anacidic value. However, the list of raw materials that can be used is notlimited to the above materials, and materials produced by subjectingfish skin or fish scales to a solubilization treatment can also be used.The collagen material for use in the present invention includesmaterials which have an isoionic point that is sufficiently removed fromthe neutral region that is ideal for cosmetics, either toward the lowside (acidic) or toward the high side (alkaline), and which are highlysoluble in water in the neutral region but solidify within organicsolvents. Provided these conditions are satisfied, synthetic collagencan also be used.

The present invention relates to solubilized collagen fibers that can beused to obtain a solubilized collagen for use as a cosmetic.Specifically, the present invention relates to the solubilized collagenfibers described below.

Namely, the solubilized collagen fibers include a solubilized collagensolid content of 66 to 87 wt %, a buffer salt content of 2 to 6 wt %, awater content of 10 to 22 wt %, and a residual hydrophilic organicsolvent content of a trace amount to 6 wt % (totaling 100 wt %), whereinthe average fineness of the solubilized collagen fibers is 3 to 10 dtx,the isoionic point is 4.5 to 5.0, and the aforementioned water contentof 10 to 22 wt % and the residual hydrophilic organic solvent content ofa trace amount to 6 wt % exist uniformly along the length direction ofthe fibers.

The buffer salt is selected from among sodium citrate, sodium lactateand sodium phosphate.

The solubilized collagen solid content mentioned above refers to thesolid fraction composed of solubilized collagen that corresponds withthe solubilized collagen contained in the solubilized collagen fiberbundle obtained by decomposing the collagen fibers to form a solubilizedcollagen, using the solubilized collagen to produce a solubilizedcollagen aqueous solution that functions as the raw material for thesolubilized collagen fibers, performing spinning and drawing to form asolubilized collagen fiber bundle, and then drying the fiber bundle.

The buffer salt is a component that is added prior to the reaction fordecomposing the collagen fibers for the purpose of achieving pHmodification when producing the solubilized collagen aqueous solutionfrom the solubilized collagen fiber raw material. This buffer salt hasthe function of ensuring instantaneous and uniform dissolution of thesolubilized collagen fibers in water when the fibers are used as acosmetic.

As described above, the buffer salt is used for the purpose of pHmodification when the insoluble collagen is converted to solubilizedcollagen. In order to ensure rapid dissolution of the solubilizedcollagen fibers in aqueous solvents, dissolution must be performedwithin a pH region that is somewhat different from the isoionic point(pI). If the pH of the collagen or the pH of the solvent is close to thepI of the collagen, then achieving uniform dispersion and dissolutionrequires considerable time. In the case of an alkali-solubilizedcollagen, the pI is within a range from 4.5 to 5.0, and therefore a pHrange that enables rapid dissolution and is ideal for cosmetic materialsis from approximately 6 to 8. In order to prepare collagen fibers withinthis pH region, an appropriate amount of a buffer salt (such as Nalactate) is included. In order to ensure that the buffer salt isincorporated uniformly within the collagen fibers, the buffer salt isadded in advance to the raw material solution that undergoes spinning,and this enables an appropriate amount of the buffer salt to be retainedwithin the finally prepared collagen fibers.

All of the steps in the method used for decomposing the insolublecollagen fibers under alkaline conditions to obtain the solubilizedcollagen fibers of the present invention are described below.

The production apparatus of the present invention and all of the stepsdescribed in the present invention are conducted in an environment thatis maintained in a sterilized state.

(1) A step of decomposing insoluble collagen fibers under alkalineconditions and extracting a solubilized collagen aqueous solution, and astep of performing pH modification to produce a solubilized collagenaqueous solution that functions as a solubilized collagen fiber rawmaterial:

A step of subjecting a product obtained by decomposing a skin samplecontaining insoluble collagen fibers under alkaline conditions to aneutralization and desalting treatment, separating the neutralized anddesalted skin sample, and subsequently extracting a solubilized collagenaqueous solution having an isoionic point of pH 5.0 or less, and a stepof adjusting the pH of the solubilized collagen aqueous solution in thepresence of a buffer to a value within a range from 6.0 to 7.5 which isgreater than the isoionic point, thus preparing a solubilized collagenaqueous solution that functions as a solubilized collagen fiber rawmaterial.

These steps are described below in further detail.

A method of treating insoluble collagen fibers with a material obtainedby adding a small amount of an amine or an analog thereof to an aqueoussolution containing both a caustic alkali and sodium sulfate (forexample, see JP 46-15033 B, hereafter this method is referred to as the“alkali treatment method”) is described below.

The dermic layer is extracted from the raw hide containing the insolublecollagen that functions as the raw material, and a wet grinding mill isused to convert the dermic layer to a paste form that undergoes reactionmore readily.

In the alkali treatment method, a strong alkaline composition containingapproximately 4 to 5% of sodium hydroxide, approximately 10 to 12% ofsodium sulfate, and approximately 1% of monomethylamine (wherein theabove numbers represent weight concentrations within the solution) isused as the alkali treatment agent.

The sodium hydroxide within the strong alkaline composition decomposesthe peptides of the collagen crosslinked portions (telopeptides),thereby cleaving the crosslinks and solubilizing the collagen. Thesodium sulfate is used for preventing swelling of the collagen by thealkali, and preventing decomposition of the main chain portion (thetriple helix portion) of the collagen. If the monomethylamine is notused, then the solubilization tends to be unsatisfactory, and a hardviscous solution (containing a large amount of multimers) is obtained.

During the solubilization treatment, it is necessary to ensure thatdenaturation of the collagen and precipitation of the sodium sulfate donot occur, and therefore the temperature of the solubilization treatmenttank is maintained within a range from 22° C. to 27° C.

The above treatment yields a product containing an eluted solubilizedcollagen. By subjecting this product to a neutralization and desaltingtreatment, the skin that was unable to be treated is retained asneutralized and desalted skin, and this neutralized and desalted skincan be separated by a solid-liquid separation using a net-like devicethat allows the passage of water, such as a sieve. Alternatively, theneutralized and desalted skin can be separated by a centrifugalseparation method using a low centrifugal force.

As a result of the solid-liquid separation, a solution containingsolubilized collagen can be extracted. This solution is then washed toobtain the targeted solubilized collagen.

In the alkali treatment, the isoionic point of the obtained collagen isfrom 4.5 to 5.0. This is because the asparagine residues and glutamineresidues in the collagen undergo a deamidation (releasing free ammonia)in the presence of the alkali, and are converted to aspartic acidresidues and glutamic acid residues respectively.

Cosmetic items are preferably within a range from slightly acidic toneutral, and therefore during preparation of the solubilized collagenfiber raw material for use in cosmetics, no dramatic change is requiredin the isoionic point of the solubilized collagen. The collagenconcentration is generally from approximately 3 wt % to 6 wt %.

The pH of the solubilized collagen aqueous solution is adjusted in thepresence of a buffer to a value within a range from 6.0 to 7.5 which isgreater than the isoionic point, thus preparing a solubilized collagenaqueous solution that functions as the solubilized collagen fiber rawmaterial.

Following preparation of the solubilized collagen fibers, adjusting thepH of the solubilized collagen aqueous solution that functions as thesolubilized collagen fiber raw material is effective in obtaining asolubilized collagen aqueous solution that can be used as a cosmetic.

The reasons for this observation are as follows.

Collagen is an amphoteric electrolyte, and has a property wherein theelectric charge varies depending on the pH. The pH at which the positiveand negative charges are in equilibrium, resulting in an apparent chargeof zero, is the isoionic point. At this pH, the solubility of collagendeteriorates and aggregation tends to occur. Accordingly, in order toimprove the solubility in the neutral region that is desirable forcosmetics, it is important that the isoionic point is somewhat removedfrom the neutral region. In the present invention, performing the alkalitreatment alters the isoionic point to a value of 4.5 to 5.0.Alternatively, a method may be employed in which collagen having anisoionic point of approximately 7 to 8 obtained from a solubilizationtreatment that uses a protease enzyme is subjected to a chemicaltreatment such as succinylation to lower the isoionic point. Thesolubilization is performed to enable spinning of the obtained collagen.If the pH is held at the isoionic point, then dissolution is impossible,and therefore the solubilization must be performed on either the acidicside or the alkali side of the isoionic point. However, when solutionpreparation is performed on the acidic side of the isoionic point (forexample, pH 3), then when an attempt is made to subsequently dissolvethe obtained dried fibers in a neutral aqueous liquid (for example, pH7) for use as a cosmetic, because the pH must pass through the isoionicpoint, aggregation may occur and dissolution takes a considerable lengthof time, meaning use as a cosmetic is problematic. On the other hand,when the solution is prepared on the alkali side of the isoionic point,and particularly at a pH within a range (pH 6.0 to 7.5) that is close tothat at which final dissolution of the dried fibers occurs, the solutionneed not pass through the isoionic point, and the collagen remains in areadily dissociated state, meaning rapid dissolution can be achieved,and collagen fibers that are ideal for use as cosmetics can be obtained.

(2) A step of subjecting the solubilized collagen aqueous solution thatfunctions as the solubilized collagen fiber raw material to spinning anddrawing to produce a solubilized collagen fiber bundle:

A step of discharging the solubilized collagen aqueous solution obtainedin (1) above into an organic solvent in a thread-like form, spinning thesolubilized collagen into a fiber bundle, drawing the spun solubilizedcollagen fiber bundle by winding, and then immersing the drawnsolubilized collagen fiber bundle in a hydrophilic organic solvent.

Specifically, this step is conducted in the manner described below.

FIG. 1 is a diagram illustrating one example of a production apparatusfor producing the type of solubilized collagen fibers described above.

This production apparatus 1 comprises a piston tank 5, which holds asolubilized collagen aqueous solution A and supplies the solubilizedcollagen aqueous solution A, a first solvent tank 3 containing anorganic solvent S1 composed of isopropanol into which the suppliedsolubilized collagen is discharged via a nozzle 7 having a plurality ofdischarge holes, and in which the discharged collagen is spun and thendrawn, enabling the extraction of solubilized collagen fibers containingwater, a winding roller 11 which is wound at a predetermined windingrate and is used for drawing and extracting the fibers in the form ofsolubilized collagen fibers having a water content, and a second solventtank 13 containing a hydrophilic organic solvent S2 into which thesolubilized collagen fibers containing water that have been wound by theroller 11 are supplied.

Further, the supply of the solubilized collagen aqueous solution A fromthe piston tank 5 through the nozzle 7 is performed through the actionof a gear pump 9. The winding roller 11 is used for winding the spunsolubilized collagen fibers at a predetermined winding rate.

The piston tank 5 and the nozzle 7 are connected, via the gear pump 9,by a plastic conduit. In this example, the first solvent tank 3 has anelongated shape of a prescribed length, and the nozzle 7 is installed atone end of the first solvent tank 3 with the discharge holes directed inthe horizontal direction, enabling the collagen aqueous solutiondischarged from the nozzle 7 to travel horizontally through the organicsolvent S1 along the length of the first solvent tank 3 to the other endof the first solvent tank 3.

When the solubilized collagen aqueous solution is discharged into theorganic solvent and solidified, the organic solvent used may be either ahydrophilic organic solvent or a hydrophobic organic solvent.

The solubilized collagen aqueous solution discharged into the organicsolvent solidifies instantaneously to form fibers as the water diffuseswithin the organic solvent. In terms of facilitating the diffusion ofthe water contained within the collagen aqueous solution away from thefibers, a hydrophilic organic solvent is particularly suitable.

In order to enable efficient drying of the solidified fibers, the use ofa solvent that enables the water to be evaporated from a state thatincorporates water is desirable. In this regard, the use of ahydrophilic organic solvent is preferred. Specific examples of solventsthat can be used include alcohols such as methanol, ethanol, andisopropanol, and acetone. A mixed solvent containing a plurality ofdifferent solvents may also be used. From a practical perspective, anorganic solvent containing a small amount of water can also be used, andin such cases, the water content within the solvent is typically notmore than approximately 15 wt % and preferably 10 wt % or less. If thewater content is too high, then the collagen cannot be solidifiedfavorably.

In the production apparatus 1 illustrated in FIG. 1, when the piston ofthe piston tank 5 is pressurized using compressed air, and the gear pump9 is activated, the solubilized collagen aqueous solution A is suppliedfrom the piston tank 5 to the nozzle 7, and is then discharged into theorganic solvent S1 inside the first solvent tank 3 from the plurality ofcircular discharge holes in the nozzle 7.

The solubilized collagen is discharged into the organic solvent from theplurality of circular discharge holes in the nozzle 7, solidification ofthe solubilized collagen proceeds from the external surface toward theinterior, resulting in fiber formation, and by pushing the collagen outin a horizontal direction, the plurality of collagen fibers are spuninto a bundle while also undergoing a drawing treatment. The formedbundle of the solubilized collagen fibers F is pulled out of the organicsolvent Si by a pulley located at the other end of the first solventtank 3, and is then wound around a winding roller 11.

At this time, by setting the winding rate of the winding roller 11 to afaster rate than the discharge rate from the nozzle 7, the spunsolubilized collagen fibers F are stretched while solidifying, and formnarrow fibers having an average fineness of 10 dtx. The lower limit forthe average fineness has been confirmed as low as 3 dtx.

During the period required for the collagen fibers to solidify, orspecifically during the period required for the exterior of the collagenfibers to solidify, spinning and drawing of the collagen fibers isperformed. During this period, the collagen fibers exist within theorganic solvent, and therefore the water content within the collagenfibers is substituted with the organic solvent.

The time required for solidification varies depending on the finenessand the like of the fibers undergoing spinning. Considering suchfactors, the time required for solidification of the solubilizedcollagen fibers is generally set to approximately 8 seconds.

If a value of approximately 5 m/minute is used for the winding rate ofthe winding roller 11, then the length of the first solvent tank 3 inthe direction of operation must be approximately 70 cm or longer.

By discharging the solubilized collagen aqueous solution through thenozzle and into the organic solvent, the solubilized collagen can bespun.

This spinning can be achieved by using a device such as a nozzle orshower head which has discharge holes that can discharge a fluid in afiber-like form and can therefore disperse and release the fluid. Thesolubilized collagen aqueous solution, which has a solubilized collagenconcentration from 2 to 10 wt %, and preferably from 3 to 7 wt %, isdischarged into the organic solvent at a rate of 20 to 500 g/minute, andpreferably 30 to 150 g/minute, through a dispersion release devicehaving a hole diameter of approximately 0.05 to 1 mm, and preferablyapproximately 0.05 to 0.3 mm. As a result, solubilized collagen fibershaving an average fineness of approximately 10 to 100 dtx (measured at20° C. and 65% RH using a fineness meter) can be formed.

The thickness of the solubilized collagen fibers can be narrowed byadjusting the concentration of the discharged solubilized collagenaqueous solution, or by appropriate selection of the hole diameter ofthe discharge nozzle. If the concentration of the solubilized collagenaqueous solution is too low, then the spun fibers tend to rupture moreeasily, and a powder-like solid tends to be produced. If the nozzle holediameter is too narrow, then the flow resistance increases, and anexcessively large discharge pressure occurs at the nozzle. Consequently,the collagen fibers discharged from the nozzle in a free state undergoshrinkage in the fiber length direction during solidification, shrinkingto less than approximately 0.6 times the original length and resultingin an increase in the fineness.

There is a limit to how far the fineness can be reduced using themethods of narrowing the nozzle hole diameter and reducing theconcentration of the solubilized collagen aqueous solution.

In one method of resolving this problem, the collagen fibers that arespun in the solvent can be wound at a rate that is at leastapproximately 0.6 times the discharge rate. By using this method, thepulling force applied to the collagen fibers during spinning actsagainst the shrinkage in the fiber length direction, thereby drawing thefibers and enabling the preparation of fine fibers of 10 dtx or less. Asa result of the drawing, the collagen fibers are collected in thehydrophilic organic solvent S2 inside the second solvent tank 13 as afiber bundle that is free of twisting and curling.

By performing the spinning step in the organic solvent, the pigskin-derived lipids contained within the solubilized collagen aqueoussolution are eluted into the organic solvent, thereby reducing the lipidcontent to approximately 0.1 wt % and yielding a high-purity collagen. Aportion of the buffer is also eluted, but the buffer that is retainedwithin the fibers has the effect of increasing the dissolution rate whenthe dried solubilized collagen fibers are dissolved in water.

If the concentration of the hydrophilic organic solvent in the firstsolvent tank 3 is maintained at a satisfactorily high level, then thefiber bundle need not necessarily be passed through the second solventtank, and the fiber bundle leaving the winding roller 11 may be guideddirectly between nip rollers 31 and subjected to continuous spinning anddrying.

In the spinning step, if the winding rate is too fast, then the fibersare prone to rupture, and therefore drawing is performed with the ratioof the winding rate relative to the discharge rate (namely, the draft)adjusted to a value of 1.5 or less.

Considering the above factors, ideal conditions for spinning collagenfibers having an average fineness of 10 dtx or less include a collagenaqueous solution concentration of 3 to 7 wt %, and preferably 3.5 to 5wt %, a nozzle hole diameter of 0.05 to 0.18 mm, and preferablyapproximately 0.09 to 0.11 mm, and a draft of at 0.6 to 1.5, andpreferably 1.0 to 1.2.

Each of the various conditions may be set within the respective rangedescribed above, in accordance with a formula 2 shown below.

T=100·r ² cd/D  Formula 2

In this formula, T represents the fineness (dtx), r represents thenozzle hole radius (mm), c represents the collagen aqueous solutionconcentration (wt %), d represents the collagen specific gravity (g/ml),and D represents the draft.

In terms of the types of numerical values that are actually employed,setting the various values so as to achieve a discharge rate ofapproximately 2 to 7 m/minute and a winding rate of approximately 2 to10 m/minute is practical.

The wound solubilized collagen fibers are dried in a sterilizedenvironment by air drying using sterilized air. This removes anyresidual water. In the case of the types of fine fibers produced in thepresent invention, if the fibers are in mutual contact and drying isperformed in this state, then the fibers tend to adhere and bondtogether, forming a fibrous lump.

The reason for this observation is that because the organic solvent isremoved first during drying, the residual water content contained withinthe solubilized collagen fibers re-dissolves the solidified collagen,and therefore as the fibers become finer, adhesion of the fibers becomesmore significant.

In order to prevent this adhesion, in the present invention, thesolubilized collagen fibers are immersed in a hydrophilic organicsolvent prior to drying. By bringing the fibers into contact with thehydrophilic organic solvent, the water content within the collagenfibers diffuses within the organic solvent and is replaced with theorganic solvent, meaning the water content of the fibers decreases andthe organic solvent content increases. As a result, adhesion of thefibers during drying is reduced.

The water content of the hydrophilic organic solvent used for immersionmust be low, and specifically, an organic solvent having a water contentof 5 wt % or less is typically used. Specific examples of hydrophilicorganic solvents that can be used include alcohols such as methanol,ethanol, and isopropanol, and acetone. A mixed solvent containing aplurality of these types of solvents may also be used. In order to avoidthe retention of only water during the drying of the collagen fibers,the use of a solvent having a boiling point close to that of water, or asolvent that undergoes azeotropic distillation with water is effective,and specific examples of such solvents include ethanol and isopropanol.

When the spun solubilized collagen fibers are immersed in thehydrophilic organic solvent, the water content of the hydrophilicorganic solvent increases. Once the organic solvent has been used forrepeated immersion treatments, and the water content of the solvent hasbecome excessive, the organic solvent must be replaced. Subjecting thesolubilized collagen fibers to a light compression or centrifugaldewatering treatment to reduce the amount of liquid contained within thefibers immediately prior to immersion in the organic solvent iseffective in reducing the frequency with which the immersion organicsolvent must be replaced.

If a value of approximately 5 m/minute is used for the winding rate ofthe winding roller 11, then the length of the first solvent tank 3 inthe direction of operation must be approximately 70 cm or longer.

(3) A step of drying the solubilized collagen fiber bundle obtained in(2) to produce solubilized collagen fibers for cosmetics

A step of drying the solubilized collagen fiber bundle to produce thetargeted solubilized collagen fibers by passing the above solubilizedcollagen fiber bundle through nip rollers, introducing the resultingsolubilized collagen fiber bundle having a reduced water content and areduced concentration of the hydrophilic organic solvent into a dryingtube, forming a moving bed of air inside the tube by blowing sterilizedair having a temperature of 30° C. or lower into the tube, using themoving bed of air to move and dry the solubilized collagen fiber bundleinside the tube, and then extracting the solubilized collagen fiberbundle from the tube.

A complete drying apparatus used in the present invention for drying thespun and drawn solubilized collagen fiber bundle is illustrated in FIG.3.

Prior to drying the spun and drawn solubilized collagen fiber bundleusing air from an air supply device 33, the spun and drawn solubilizedcollagen fiber bundle is passed between the nip rollers 31 to squeeze aportion of the water content and alcohol content from the spun and drawnsolubilized collagen fiber bundle, thereby reducing the water contentand the alcohol content within the spun and drawn solubilized collagenfiber bundle. The water and alcohol that has been squeezed from thefiber bundle is collected in a liquid collection device 35. This liquidis stored in a collected liquid storage device 36 (not shown in thedrawings).

Because a portion of the water and alcohol contained within the spun anddrawn solubilized collagen fiber bundle can be removed prior to thedrying with air, the operation of passing the spun and drawn solubilizedcollagen fiber bundle through the nip rollers 31 is an importantpretreatment to the drying operation of drying the spun and drawnsolubilized collagen fiber bundle using the air supplied from the airsupply device 33.

Following squeezing of a portion of the water and alcohol containedwithin the spun and drawn solubilized collagen fiber bundle by passingthe fiber bundle between the nip rollers 31, the solubilized collagenfibers are introduced into a drying tube (tube-shaped drying device) 32and dried within a stream of air. The air used for the drying passesthrough the air supply device 33, is filtered, cleaned and sterilized bypassage through a filter 34 (such as a high-efficiency particulate airfilter), and in consideration of enabling stable drying of thesolubilized collagen fiber bundle at a temperature of 30° C. or lower,is preferably supplied to the drying tube (tube-shaped drying device) 32with the temperature maintained at 20° C. or lower. By supplying the airwith the temperature maintained at a specific temperature or lower, theair can be distinguished from the air of the surrounding environment.The air supplied to the drying tube (tube-shaped drying device) 32 issupplied at a uniform rate. If the tube-shaped drying device 32 isconstructed in the form of an aspirator, then the collagen fibers can befed into the drying device from the suction port. Another effectivemethod involves using a commercially available air gun designed forsuctioning and transporting powders and granules (such as the air gunsMAG-22S, MAG-22SV, MAG-22L and MAG-22LV manufactured by Trusco NakayamaCorporation, details of the structures of which are included in theoperating manuals available from the manufacturer), and feeding thecollagen fibers through the suction port.

The air is supplied at a temperature within a range from 30° C. to 0° C.If the temperature exceeds 30° C., then there is a concern that thecollagen may undergo denaturation. Further, if the temperature is lowerthan 0° C., then the drying efficiency deteriorates.

The humidity must be 70% or less. If the humidity exceeds 70%, then thefibers are more likely to adhere. There are no disadvantages associatedwith a low humidity.

Movement of the solubilized collagen fiber bundle inside the drying tube(tube-shaped drying device) 32 is caused by the sterilized air having atemperature described above. The actual rate of this movement isdependent on the feed rate through the nip rollers. By appropriatecontrol of the combination of this feed rate and the air flow rate,treatment can be conducted under ideal drying conditions (namely,conditions which not only yield favorable drying, but also result in theproduction of fibers with an appropriate level of crimping, and minimaladhesion and twisting of the fibers). In those cases where apolyethylene tube having a diameter of 19 mm and a length of 3 m isused, performing drying under conditions including a collagen feed rateof 2 to 3.5 m/minute and an air flow rate of 200 to 300 L/minute yieldsa dry solubilized collagen fiber bundle having minimal fiber adhesionand having a favorable wave applied to the entire bundle.

The change in state of the solubilized collagen fiber bundle in thedrying apparatus is indicated by the following two examples of analysisresults.

(1) Prior to supply to the nip rollers, the solubilized collagen fiberbundle and the like has a solid fraction concentration of 15 to 25 wt %,and a residual alcohol concentration of 70 to 80 wt %.

(2) Following passage through the nip rollers, the solubilized collagenfiber bundle and the like has a solid fraction concentration of 27 to 35wt %, and a residual alcohol concentration of 65 to 68 wt %.

At the outlet from the drying tube, the solubilized collagen fiberbundle and the like from (1) and (2) above has a solid fractionconcentration of 85 to 88 wt %, and a residual alcohol concentration of1.0 to 6.0 wt %.

The reason for these final results is because the nip rollers operationis able to alter each of the concentrations as described above, andbecause conventional apparatus included no appropriate device forperforming such drying, adjustment of the above concentration ranges wasimpossible. It can be stated that the drying method employed in thisinvention is very innovative.

The obtained fibers have a finished state at the tube outlet in whichthe solubilized collagen fiber bundle has a solid fraction concentrationof 85 to 88 wt % and a residual alcohol concentration of 1.0 to 6.0 wt%, and the aforementioned water content of 10 to 22 wt % and theresidual alcohol concentration of a trace amount to 6.0 wt % existuniformly along the length direction of the fibers.

By subjecting the solubilized collagen fiber bundle at the tube outletto a further drying operation, the residual alcohol concentration can bereduced to 0.01 wt % or less.

Because the bundle of the solubilized collagen fibers F is dried withoutapplication of a pulling load, a fiber bundle composed of crimpedsolubilized collagen fibers can be obtained. Moreover, by performingappropriate defibration, a fibrous state solubilized collagen can beobtained. Provided the length of the fibers is at least 2.5 cm, thefibers are intertwined, and by defibrating a fiber bundle of anappropriate length, a solubilized collagen fibrous material can beobtained.

Following completion of the drying operation, the solubilized collagenfiber bundle is subjected to fiber opening. Specifically, an openingdevice combining a plurality of wire drums is used to disentangle thefiber bundle, generating a fibrous state. The long solubilized collagenfibers that constitute the aforementioned solubilized collagen fiberbundle are broken up by the wire drums to form fibers having a length of1 to 20 cm, and these fibers are entangled to form a fibrous state, sothat a sheet having a uniform density is discharged, enabling collectionof opened solubilized collagen fibers that can be used as solubilizedcollagen fibers for cosmetics.

All of the steps in the method used for decomposing the insolublecollagen fibers using a protein degrading enzyme (protease) to obtainthe solubilized collagen fibers of the present invention are describedbelow.

(1) A combination of a step of decomposing insoluble collagen fibersusing a protein degrading enzyme (protease) and extracting a solubilizedcollagen aqueous solution, and a step of performing pH modification toprepare a solubilized collagen aqueous solution that functions as asolubilized collagen fiber raw material. Specifically, a step ofdecomposing a skin sample containing insoluble collagen fibers using aprotein degrading enzyme (protease) and extracting an insoluble collagenaqueous solution having an isoionic point of 7 to 8, and a step ofadjusting the pH in the presence of a buffer to a value within a rangefrom 6.0 to 7.5 which is greater than the isoionic point, thus preparinga solubilized collagen aqueous solution that functions as thesolubilized collagen fiber raw material.

The method using a protease is disclosed, for example, in JP 44-1175 B,and the present invention incorporates this description. Hereafter, thismethod is also referred to as an enzyme treatment method.

In the enzyme treatment method, approximately 1 kg of insoluble collagenfibers is prepared with a substrate concentration of approximately 2%,the pH is adjusted to 3 with lactic acid, and in those cases where anacidic protease is used as the protein degrading enzyme, treatment isperformed by adding the protease in an amount of 1% relative to thesubstrate. The mixture is stirred at a temperature of 25° C. using astirrer to allow the reaction to proceed.

When solubilization is performed using the enzyme treatment method, theisoionic point of the obtained collagen product is from 7 to 8. In orderto collect the collagen from the obtained product, the product of thesolubilization treatment is subjected to sedimentation using acentrifugal separation treatment with a large centrifugal force.

The isoionic point of the collagen is from 7 to 8, and in order toobtain a solubilized collagen raw material for use as a cosmetic, thecollagen is precipitated and collected by reducing the pH to 5 or lower.In order to achieve an ideal pH for use as a cosmetic, the final pH isadjusted to a value from approximately 6.0 to 7.5. Sodium hydroxide andsodium lactate are added as a buffer.

In a solubilized collagen product obtained using a typical enzymetreatment method, a succinylation is performed to lower the isoionicpoint and enhance the solubility under neutral conditions, and thistreatment can be used favorably in producing a solubilized collagen bythis type of method.

The above step (1) can be performed in the manner described below.

(1) A step of decomposing insoluble collagen fibers using a proteindegrading enzyme (protease) and extracting a solubilized collagenaqueous solution, and a step of performing pH modification to prepare asolubilized collagen aqueous solution that functions as a solubilizedcollagen fiber raw material.

Namely, a step of adding an alkali to a product containing collagen,obtained by decomposing a protein containing insoluble collagen using aprotease and having an isoionic point of 7 to 8, to adjust the pH of theproduct to 9 to 10, using a carboxylic anhydride to succinylate thesolubilized collagen and reduce the pH to 5 or less, and subsequentlyprecipitating and separating the solubilized collagen. In order to thenprepare a solubilized collagen aqueous solution, an alkali is added inthe presence of a buffer to adjust the pH to a value within a range from6.0 to 7.5 which is greater than the isoionic point.

(2) A step of spinning and drawing the solubilized collagen aqueoussolution that functions as the solubilized collagen fibers raw materialto produce a solubilized collagen fiber bundle.

Namely, a step of discharging the solubilized collagen aqueous solutionobtained in (1) above into an organic solvent in a thread-like form,spinning the solubilized collagen into a fiber bundle, drawing the spunsolubilized collagen fiber bundle by winding, and then immersing thedrawn solubilized collagen fiber bundle in a hydrophilic organicsolvent.

This step is performed using the same method as that described above for(2) in relation to the alkali treatment.

(3) A step of drying the solubilized collagen fiber bundle obtained in(2) to produce solubilized collagen fibers for cosmetics.

Namely, a step of drying the solubilized collagen fiber bundle toproduce the targeted solubilized collagen fibers by passing the abovesolubilized collagen fiber bundle through nip rollers, introducing theresulting solubilized collagen fiber bundle having a reduced watercontent and a reduced concentration of the hydrophilic organic solventinto a drying tube, forming a moving bed of air inside the tube byblowing sterilized air having a temperature of 30° C. or lower into thetube, using the moving bed of air to move and dry the solubilizedcollagen fiber bundle inside the tube, and then extracting thesolubilized collagen fiber bundle from the tube.

This step is performed using the same method as that described above for(3) in relation to the alkali treatment.

In those cases where the water medium is mainly pure water, thesolubilized collagen fibers dissolve readily in the pure water due tothe action of the buffer incorporated within the solubilized collagenfibers. Further, by adding a small amount of an electrolyte such as anacid, base, neutral salt or buffer salt to the solubilized collagenfibers, the fibers are able to be dissolved satisfactorily withinaqueous liquids. In particular, if a buffer salt such as sodium citrate,sodium lactate or sodium phosphate (namely, a salt of a weak acid and aweak base) that stabilizes the pH in a range from slightly acidic toneutral is added to the aqueous liquid to adjust the pH of the aqueousliquid to a value of approximately 5.5 to 9.0, then the solubilizedcollagen fibers can be more readily dissolved. The solubilized collagenfibers can be dissolved in short period of 30 seconds or less. If anexcessive amount of the salt is added, then a salting-out effect makesit difficult to dissolve the collagen in aqueous liquids. Theelectrolyte may be incorporated within an aqueous solution.

In regard to this point, because total desalting of the solubilizedcollagen has not occurred following the solubilization treatment,residual electrolyte exists within the solubilized collagen. In thiscase, the solubilized collagen may also be used in this state, with nofurther modification.

Any of the various components typically added to solubilized collagenfibers for use in cosmetics may be added to the aqueous liquid, providedthis addition does not impair the dissolution of the solubilizedcollagen in an aqueous solution. Examples of these components includemoisturizing agents such as butanediol, pentanediol, glycerol,hyaluronic acid and urea, preservatives such as methyl p-hydroxybenzoateand phenoxyethanol, plant extracts such as aloe extract, alcohol-basedsolvents such as ethanol, ultraviolet absorbers, vitamins,anti-inflammatory agents, oils and fats such as olive oil, fatty acids,and any of the various functional components that have a specificcosmetic function.

By setting the combination ratio between the collagen fibers and theaqueous liquid so that the collagen content within the obtained cosmeticmaterial is approximately 0.01 to 10 wt %, and particularlyapproximately 0.1 to 3 wt %, a uniformly dissolved cosmetic material canbe obtained rapidly.

Examples of the aqueous solutions that can be used include commerciallyavailable toilet waters and cosmetic liquids.

Because of their favorable properties, the solubilized collagen fibersfor cosmetics and fiber balls according to the present inventiondissolve rapidly in commercially available toilet waters and cosmeticliquids. Accordingly, the user may select a toilet water or cosmeticliquid depending on individual preference, and then combine thisselected water or liquid with the solubilized collagen fibers or fibrousmaterial for cosmetic use, thus preparing a solubilized collagensolution for cosmetic use. Accordingly, a solubilized collagen cosmeticmaterial that satisfies the needs of the user can be provided to theuser in a fresh state whenever it may be required. Depending on thestate of the skin of the user, a cosmetic that is suitable for that skinstate can be prepared. The type of cold-temperature storage required forconventional solubilized collagen cosmetics is unnecessary, and the timerequired for preparing the cosmetic material is short, meaning there isno time restriction associated with use of the product, and the productmay simply be used in accordance with the needs of the user.

Following dissolution, the collagen cosmetic material is prone todenaturation in a similar manner to that observed for typical collagencosmetics in the form of aqueous solutions. However, the aforementionedtreatment in which an alcohol was used as the organic solvent during thepreparation of the solubilized collagen fibers has a sterilizationeffect on the collagen, and therefore the resulting solubilized collagenfibers, which are obtained by drying with sterilized air, are notcontaminated with unwanted bacteria. Moreover, compared with collagen ina solution state, solubilized collagen in a dried state is significantlymore resistant to the proliferation of bacteria or mold or the like,meaning the level of treatment required to preserve the product duringtransport can be reduced. Cosmetic materials that contain almost nocomponents other than the collagen, including components such aspreservatives, can be used.

Similarly, in the case of aqueous liquids for use as cosmetics, becauseseparation is performed from collagen having a high nutritional value,the amount of added preservatives can be reduced, and the level ofpreservation treatment required can be reduced. Further, aqueous liquidscan be sterilized more easily than collagen, and therefore bysterilizing the aqueous liquid and using aseptic packaging, the additionof preservatives becomes unnecessary.

The solubilized collagen fibers of the present invention may be marketedin the form of a fiber bundle, subjected to fiber opening and thenmarketed as individual fiber balls, or marketed as a combination ofsolubilized collagen fibers for cosmetic use and an aqueous liquid, withthe fibers and the liquid provided in separated containers.

By dividing the solubilized collagen fibers into individual packagescontaining the amount of fibers required for a single use, measuring theamount of fibers at the time of use becomes unnecessary, and if acontainer containing a solubilized collagen fiber bundle or fibrousmaterial equivalent to a single use is marked with a level indicatingthe amount of aqueous liquid that is required, then the user can easilymeasure out the amount of toilet water or the like when preparing thecosmetic material, meaning a favorable cosmetic material can be obtainedon each occasion.

Further, if the aqueous liquid and the solubilized collagen fiber bundleor fibrous material are placed in a soft container having two separatecompartments that are separated by a partition that can be broken byapplication of light force, then the solubilized collagen fibers can bemixed with and dissolved in the aqueous liquid by breaking thepartition.

EXAMPLES

The solubilized collagen fibers for cosmetics according to the presentinvention and the production thereof are described below in furtherdetail, with reference to a series of examples.

Example 1

Samples of solubilized collagen fibers for cosmetics were prepared inthe manner described below, and the time required for dissolution wasmeasured. The isoionic point of the solubilized collagen fibers wasconfirmed in the manner described below.

(Measurement of Isoionic Point)

A cationic exchange resin (Amberlite IPR-120B, manufactured by OrganoCorporation) and an anionic exchange resin (Amberlite IPA-400,manufactured by Organo Corporation) that had been activated and washedin advance were mixed in a ratio of 2:5 to prepare a mixed bed ionexchanger. Subsequently, 100 ml of this mixed ion exchanger was broughtto equilibrium using deionized water, 50 ml of a sample solutionprepared with a protein concentration of 5% was added to the ionexchanger, and the mixture was held at 40° C. in a water bath andstirred gently for 30 minutes. The supernatant was then removed from themixture, the pH of the supernatant was measured, and this measured valuewas used as the isoionic point (see the method described by J. W. Janus,A. W. Kenchington and A. G. Ward, Research, Vol.4, 247-248 (1951)).

(Sample 1)

Preparation of Solubilized Collagen Aqueous Solution

Using wet-salted pig hide as a raw material, liming was performed.Specifically, one half of a single wet-salted pig hide (approximately 4kg) was cut into small skin pieces approximately 3 cm square, an amountof water equivalent to 300% of the weight of the skin pieces and 0.6% ofa nonionic surfactant were added and stirred to wash the skin pieces,and the skin pieces were then recovered. Subsequently, the skin pieceswere combined with an amount of water equivalent to 300% of the weightof the skin pieces, together with 0.6% of a nonionic surfactant and0.75% of sodium carbonate, the mixture was stirred for 2 hours, and theskin pieces were once again recovered. Next, the recovered skin pieceswere washed twice with amounts of water equivalent to 700% of the weightof the skin pieces, and the skin pieces were then combined with anamount of water equivalent to 300% of the weight of the skin pieces,together with 0.15% of a nonionic surfactant, 3.6% of sodiumhydrosulfide, 0.84% of sodium sulfide and 2.4% of calcium hydroxide, themixture was stirred for 16 hours, and the skin pieces were once againrecovered and washed three times with amounts of water equivalent to700% of the weight of the skin pieces.

Next, 8,000 g of an aqueous solution was prepared containing 6 wt % ofsodium hydroxide, 15 wt % of sodium sulfate and 1.25 wt % ofmonomethylamine, and then 2,000 g of the above skin pieces (a dried wtof approximately 500 g) were added to the solution and stirredthoroughly.

The resulting mixture was held inside a sealed container at 25° C., andincubated for 5 days to solubilize the collagen. With the aqueoussolution undergoing gentle stirring, an amount of sulfuric acid equal tothe amount of alkali within the aqueous solution was added dropwise toneutralize the solution, thereby adjusting the pH to 4.8.

Following neutralization, the skin pieces were removed and pressed toremove any liquid contained therein, and the skin pieces weresubsequently stirred for 30 minutes in approximately 8,000 g of anaqueous solution of lactic acid with a pH of 5.0, and then pressed anddewatered. This operation was repeated a further 4 times to achievesatisfactory desalting. In a neutralized state, the pH of the skinpieces is close to the isoionic point of the solubilized collagen, andtherefore although the collagen is solubilized, it undergoes almost nodissolution in water even during the desalting operations, but is ratherretained within the skin pieces.

The collagen content of the skin pieces following desalting wascalculated from the results of measuring the total nitrogen contentusing the Kjeldahl method, and based on this calculated collagen contentvalue, a sample of the desalted skin pieces equivalent to 120 g ofcollagen was mixed thoroughly with water and sodium lactate to obtain anaqueous solution having a collagen concentration of 4.4 wt % and asodium lactate concentration of 1.2 wt %, thus yielding 4,000 g of asolubilized collagen aqueous solution. Subsequently, a small amount of a20% aqueous solution of sodium hydroxide was added and stirred to adjustthe pH to a value of 6.7.

Production of Solubilized Collagen Fibers

The tank 5 of a production apparatus 1 having the structure illustratedin FIG. 1 was charged with 4,000 g of the solubilized collagen aqueoussolution obtained above, and 18 L of isopropanol was used as the organicsolvent and placed in the first solvent tank 3 having a length of 3 mand a width of 10 cm. By operating the gear pump 9, the solubilizedcollagen aqueous solution was discharged into the organic solvent fromthe discharge holes of the nozzle 7, which were directed in thehorizontal direction (hole diameter: 0.10 mm, number of holes: 1,000),at a rate of 38 g/minute (discharge rate: 4.8 m/minute). The bundle ofsolubilized collagen fibers that had undergone spinning within theisopropanol was pulled from the tank by the winding roller 11 at awinding rate of 5 m/minute, and was then immersed in the second solventtank 13 which contained 5.0 L of isopropanol.

Drying of Solubilized Collagen Fibers Using a polyethylene tube having adiameter of 19 mm and a length of 3 m as the tube-shaped drying device32, and with the feed rate of the nip rollers set to 3.5 m/minute, airat 20° C. and 55% RH was blown through the drying device at a rate of238 L/minute.

In terms of the state of the solubilized collagen fiber bundle, thefollowing two examples of analysis results were obtained.

(1) Prior to supply to the nip rollers, the solubilized collagen fiberbundle and the like had a solid fraction concentration of 15 to 25 wt %,and a residual alcohol concentration of 70 to 80 wt %.

(2) Following passage through the nip rollers, the solubilized collagenfiber bundle and the like had a solid fraction concentration of 27 to 35wt %, and a residual alcohol concentration of 65 to 68 wt %.

At the outlet from the drying tube, the solubilized collagen fiberbundle and the like from (1) and (2) above had a solid fractionconcentration of 85 to 88 wt %, and a residual alcohol concentration of1.0 to 6.0 wt %.

These results mean that the nip rollers operation was able to alter eachof the concentrations at the aforementioned outlet.

The obtained fibers had a finished state at the tube outlet in which thesolubilized collagen fiber bundle had a solid fraction concentration of85 to 88 wt % and a residual alcohol concentration of 1.0 to 6.0 wt %,and the aforementioned water content of 10 to 22 wt % and the residualalcohol concentration of a trace amount to 6.0 wt % existed uniformlyalong the length direction of the fibers.

The solubilized collagen fiber bundle and the like at the tube outlethad a solid fraction concentration of 82.1 wt % and a residual alcoholconcentration of 4.8 wt %.

A 50 g bundle of solubilized collagen fibers having an average finenessof 3.7 dtx (excluding the 10 in at either end of the fibers) and anatural level of crimping was obtained (isoionic point: pH 4.9). Almostno adhered fiber portions were observed. The fineness was measured usinga fineness meter (Deniel Computer DC-11A, manufactured by Search Co.,Ltd.), by measuring 20 fibers from each sample in an environment at 20°C. and 65% RH, and then calculating the average fineness value (thismethod was also used in example 2 onward). The pH of a 0.5 wt % solutionprepared by dissolving the solubilized collagen fibers in deionizedwater was 7.1.

The above solubilized collagen fibers were composed of 79 wt % ofsolubilized collagen, 2.3 wt % of sodium lactate, 4.8 wt % of isopropylalcohol, and 13.9 wt % of water (totaling 100 wt %). Further,measurement of the lipid content within the solubilized collagen fibersusing the “oil and fat content” hexane extraction method prescribed inJIS K6503: (2001) 5.6 yielded a result of less than 0.1 wt %.

Approximately 10 mg of the obtained solubilized collagen fibers wereplaced in the palm of the hand, 1 mL of water was added, and when mixingwas performed with the index finger, the fibers dissolved inapproximately 30 seconds, forming a state that was usable as a cosmeticmaterial.

Example 2

(Sample 2) With the exception of altering only the nip rollers feed rateto 2 m/minute, the spun solubilized collagen fibers of the sample 1(that were immersed in the second solvent tank 13) were dried under thesame conditions as those described for the example 1.

The measurement results for the solubilized collagen fiber bundle ateach of the steps within the drying treatment were as follows.

Prior to supply to the nip rollers, the solubilized collagen fiberbundle and the like had a solid fraction concentration of 20 wt %, and aresidual alcohol concentration of 74 wt %.

Following passage through the nip rollers, the solubilized collagenfiber bundle and the like had a solid fraction concentration of 30 wt %,and a residual alcohol concentration of 66 wt %.

At the outlet from the drying tube, the solubilized collagen fiberbundle and the like had a solid fraction concentration of 87.1 wt %, anda residual alcohol concentration of 1.5 wt %.

A 50 g bundle of solubilized collagen fibers having an average finenessof 3.7 dtx (excluding the 10 m at either end of the fibers) and anatural level of crimping was obtained (isoionic point: pH 4.9). Almostno adhered fiber portions were observed. The solubilized collagen fiberswere composed of 84 wt % of solubilized collagen, 2.5 wt % of sodiumlactate, 1.5 wt % of isopropyl alcohol, and 12.0 wt % of water (totaling100 wt %). The oil and fat content, measured using the hexane extractionmethod, was less than 0.1 wt %.

Approximately 10 mg (approximately 3 cm) of the obtained solubilizedcollagen fiber bundle was cut with scissors and placed in the palm ofthe hand, 1 mL of water was added, and when mixing was performed withthe index finger, the fibers dissolved in approximately 30 seconds,forming a state that was usable as a cosmetic material.

Example 3

(Sample 3)

The solubilized collagen fiber bundle of the sample 2 was subjected tofiber opening using an opening device.

From the resulting fibrous-like solubilized collagen fiber sheet, 10 mgof the solubilized collagen fibers were placed in the palm of the hand,1 mL of water was added, and when mixing was performed with the indexfinger, the fibers dissolved in approximately 20 seconds, forming astate that was usable as a cosmetic material.

Comparative Example 1

(Sample 4)

The spun solubilized collagen fibers of the sample 1 (that were immersedin the second solvent tank 13) were dried using a conventionalroller-type drying device illustrated on the left side of FIG. 2. Thedistance between the left and right rollers was 1.8 m, five stages wereemployed (drying path total length: 9 m), and air at 25° C. and 45% RHwas blown through the device at a rate of 0.5 in/second.

A 50 g bundle of solubilized collagen fibers having an average finenessof 3.7 dtx (excluding the 10 m at either end of the fibers) was obtained(isoionic point: pH 4.9). The fibers had a linear form with absolutelyno crimping, and a high degree of fiber adhesion was very noticeable.

The solubilized collagen fibers were composed of 77.8 wt % ofsolubilized collagen, 2.7 wt % of sodium lactate, 5.2 wt % of isopropylalcohol, and 14.3 wt % of water (totaling 100 wt %). The oil and fatcontent, measured using the hexane extraction method, was less than 0.1wt %.

Approximately 10 mg of the obtained solubilized collagen fibers wereplaced in the palm of the hand, 1 mL of water was added, and mixing wasperformed with the index finger, but even after 60 seconds the fibershad not completely dissolved, and a state that was usable as a cosmeticmaterial could not be obtained. This was because the adhered portions ofthe fibers did not dissolve.

Comparative Example 2

(Sample 5)

The spun solubilized collagen fibers of the sample 1 (that were immersedin the second solvent tank 13) were cut to a length of 1.2 m, and thendried using a conventional hanging-type batch drying device illustratedon the right side of FIG. 2. The spun solubilized collagen fibers werelightly stroked with the fingers to squeeze out the alcohol, weresubsequently hung over a stainless steel bar installed inside a cleanbench, and were then dried under conditions of 20° C. and 45% RH. Theair flow was generated by the exhaust flow from the clean bench.

A 50 g bundle of solubilized collagen fibers having an average finenessof 3.7 dtx (excluding the adhered portions) was obtained (isoionicpoint: pH 4.9). The solubilized collagen fibers were composed of 81.7 wt% of solubilized collagen, 2.9 wt % of sodium lactate, 3.5 wt % ofisopropyl alcohol, and 11.9 wt % of water (totaling 100 wt %). The oiland fat content, measured using the hexane extraction method, was lessthan 0.1 wt %.

The portions of the fibers within the vicinity of the contact with thestainless steel bar adhered to one another to form a bent U-shape. Fiberadhesion was also noticed within other portions of the fibers. With theexception of these adhered portions, the level of crimping wascomparatively favorable.

Approximately 10 mg of the obtained solubilized collagen fibers wereplaced in the palm of the hand, 1 mL of water was added, and mixing wasperformed with the index finger, but even after 60 seconds the fibershad not completely dissolved, and a state that was usable as a cosmeticmaterial could not be obtained. This was because the adhered portions ofthe fibers did not dissolve.

Example 4

A 10 g sample was taken from each of the solubilized collagen fibersobtained in example 1, example 2, comparative example 1 and comparativeexample 2, portions in which the fibers had adhered (namely, portionswhere the fibers could not be separated into individual fibers, butrather formed an adhered lump) were cut away, the weight of theseadhered portions was measured, and the proportion of adhered portionsrelative to the total weight of the solubilized collagen fibers wascalculated. The results were as follows.

Example 1: 1% or less

Example 2: 1% or less

Comparative example 1: 50%

Comparative example 2: 20%

It is evident that the drying method of the present invention isextremely effective in preventing fiber adhesion.

Example 5

(Sample 6)

Preparation of Solubilized Collagen Aqueous Solution

A wet-salted pig hide was cut into pieces and limed in the same manneras that described for the sample 1. The thus obtained skin pieces werefed through a chopper having a hole diameter of 16 mm, and thenconverted to a paste form using a grinding mill (Masscolloider,manufactured by Masuko Sangyo Co., Ltd.). The paste-like pig skin wassubjected to a delipidation treatment using ethanol, and was then dried.A 100 g sample was taken from the dried product, 1,900 g of deionizedwater was added, and hydrochloric acid was added to adjust the pH to 3.0while the mixture was stirred with a mixer. Subsequently, 20 g of anacidic protease formulation (Denapsin 2P, manufactured by Nagase ChemteXCorporation) was added, and stirring was continued for 24 hours at 25°C. to solubilize the collagen. The thus obtained solubilized collagenaqueous solution was adjusted to a pH of 9 to 10 by adding 2N sodiumhydroxide, 40 g of succinic anhydride was dissolved in acetone andadded, and with the temperature held at 10° C. and the pH maintainedbetween 9 and 10, reaction (succinylation) was performed for 2 hours.Following completion of the reaction, hydrochloric acid was used toadjust the pH of the reaction solution to 4.5, thus precipitating thecollagen. The precipitate was collected by performing a centrifugalseparation at 3,000 G for 10 minutes, and the precipitate was thenwashed with ethanol and dried, yielding a succinylated solubilizedcollagen dried product. To a 60 g sample of this dried product wereadded 29 g of sodium lactate and 1,920 g of water, and the mixture wasstirred to obtain a solubilized collagen aqueous solution having acollagen concentration of 4.5 wt % (pH: 6.8, sodium lactateconcentration: 1.2 wt %).

Production of Solubilized Collagen Fibers

Using the above solubilized collagen aqueous solution, solubilizedcollagen fibers were produced using the same apparatus and the sameoperations as those described for sample 1.

The measurement results for the solubilized collagen fiber bundle ateach of the steps within the drying treatment were as follows.

Prior to supply to the nip rollers, the solubilized collagen fiberbundle and the like had a solid fraction concentration of 21 wt %, and aresidual alcohol concentration of 76 wt %.

Following passage through the nip rollers, the solubilized collagenfiber bundle and the like had a solid fraction concentration of 32 wt %,and a residual alcohol concentration of 64 wt %.

At the outlet from the drying tube, the solubilized collagen fiberbundle and the like had a solid fraction concentration of 84.6 wt %, anda residual alcohol concentration of 3.0 wt %.

A 50 g bundle of solubilized collagen fibers having an average finenessof 4.1 dtx (excluding the 10 m at either end of the fibers) and anatural level of crimping was obtained (isoionic point: pH 4.5). Thesolubilized collagen fibers were composed of 83 wt % of solubilizedcollagen, 3.2 wt % of sodium lactate, 2.8 wt % of isopropyl alcohol, and11.0 wt % of water (totaling 100 wt %).

Approximately 10 mg of the obtained solubilized collagen fiber bundlewas placed in the palm of the hand, 1 mL of water was added, and whenmixing was performed with the index finger, the fibers dissolved inapproximately 30 seconds, forming a state that was usable as a cosmeticmaterial.

INDUSTRIAL APPLICABILITY

In terms of producing solubilized collagen, dissolving the solubilizedcollagen rapidly and uniformly, and then using the resulting product,the present invention enables novel trends within the fields offoodstuffs and pharmaceuticals to be used as commercial products.

DESCRIPTION OF REFERENCE SIGNS

1 Production apparatus

3 First solvent tank

5 Piston tank

7 Nozzle

9 Gear pump

11 Winding roller

13 Second solvent tank

S1 Organic solvent

S2 Hydrophilic organic solvent

A Solubilized collagen aqueous solution

F Solubilized collagen fiber bundle

21 Roller

23 Air flow

25 Hanging device

31 Nip roller

32 Tube-shaped drying device

33 Air supply device

34 Filter

35 Liquid collection device

36 Collected liquid storage device (not shown in the drawings)

37 Solubilized collagen fibers for cosmetics

38 Collection unit for solubilized collagen fibers for cosmetics

1. Solubilized collagen fibers, comprising a solubilized collagen solidcontent of 66 to 87 wt %, a buffer salt content of 2 to 6 wt %, a watercontent of 10 to 22 wt %, and a residual hydrophilic organic solventcontent of a trace amount to 6 wt % (totaling 100 wt %), wherein anaverage fineness of the solubilized collagen fibers is 3 to 10 dtx, anisoionic point is 4.5 to 5.0, and the water content of 10 to 22 wt % andthe residual hydrophilic organic solvent content of a trace amount to 6wt % exist uniformly along a length direction of the fibers.
 2. Thesolubilized collagen fibers according to claim 1, wherein the buffersalt is selected from among sodium citrate, sodium lactate and sodiumphosphate.
 3. The solubilized collagen fibers according to claim 1 or 2,obtained by a method for producing solubilized collagen fiberscomprising (i) a step of subjecting a product obtained by decomposing askin sample containing insoluble collagen fibers under alkalineconditions to a neutralization and desalting treatment, separating aneutralized and desalted skin sample, and subsequently extracting asolubilized collagen aqueous solution having an isoionic point of pH 5.0or less, and a step of adjusting pH of the solubilized collagen aqueoussolution in presence of a buffer salt to a value within a range from 6.0to 7.5 which is greater than the isoionic point, thus preparing asolubilized collagen aqueous solution that functions as a solubilizedcollagen fiber raw material; (ii) a step of discharging the solubilizedcollagen aqueous solution obtained in the step (i) into an organicsolvent in a thread-like form, spinning the solubilized collagen into afiber bundle, drawing the spun solubilized collagen fiber bundle bywinding, and then immersing the drawn solubilized collagen fiber bundlein a hydrophilic organic solvent; and (iii) a step of drying thesolubilized collagen fiber bundle from the step (ii) to produce targetedsolubilized collagen fibers by passing the solubilized collagen fiberbundle through nip rollers, introducing a thus obtained solubilizedcollagen fiber bundle having a reduced water content and a reducedconcentration of the hydrophilic organic solvent into a drying tube,forming a moving bed of air inside the tube by blowing sterilized airhaving a temperature of 30° C. or lower and a humidity of 70% RH orlower into the tube, using the moving bed of air to move and dry thesolubilized collagen fiber bundle inside the tube, and then extractingthe solubilized collagen fiber bundle from the tube.
 4. Fibrous statesolubilized collagen fibers, obtained by subjecting the solubilizedcollagen fibers according to claim 3 to fiber opening.
 5. Thesolubilized collagen fibers according to claim 1 or 2, obtained by amethod for producing solubilized collagen fibers comprising (i) a stepof decomposing a skin sample containing insoluble collagen fibersinsoluble collagen fibers using a protein degrading enzyme (protease)and extracting a solubilized collagen aqueous solution having anisoionic point of 7 to 8, and a step of adding an alkali to thesolubilized collagen aqueous solution to adjust pH to 9 to 10, using acarboxylic anhydride to succinylate the solubilized collagen and reducean isoionic point to a pH of 5 or less, subsequently precipitating andseparating the solubilized collagen, and then adding an alkali inpresence of a buffer salt to adjust p1-1 to a value within a range from6.0 to 7.5 which is greater than the isoionic point, thus preparing asolubilized collagen aqueous solution that functions as a solubilizedcollagen fiber raw material; (ii) a step of discharging the solubilizedcollagen aqueous solution obtained in the step (i) into an organicsolvent in a thread-like form, spinning the solubilized collagen into afiber bundle, drawing the spun solubilized collagen fiber bundle bywinding, and then immersing the solubilized collagen fiber bundle in ahydrophilic organic solvent; and (iii) a step of drying the solubilizedcollagen fiber bundle from the step (ii) to produce targeted solubilizedcollagen fibers by passing the solubilized collagen fiber bundle throughnip rollers, introducing a thus obtained solubilized collagen fiberbundle having a reduced water content and a reduced concentration of thehydrophilic organic solvent into a drying tube, forming a moving bed ofair inside the tube by blowing sterilized air having a temperature of30° C. or lower into the tube, using the moving bed of air to move anddry the solubilized collagen fiber bundle inside the tube, and thenextracting the solubilized collagen fiber bundle from the tube. 6.Fibrous state solubilized collagen fibers, obtained by subjecting thesolubilized collagen fibers according to claim 5 to fiber opening.
 7. Amethod for producing a solubilized collagen aqueous solution, the methodcomprising dissolving the solubilized collagen fibers according to anyone of claims 1 to 6 in an aqueous solution to obtain a solubilizedcollagen aqueous solution.